1. Field of the Invention
The present invention relates to a wrist-portable device having a thermoelectric power generator, such as a wrist watch.
2. Description of the Related Art
Of all wrist-portable devices such as wrist watches, electronic wrist watches are now the leading commodity, and most electronic wrist watches are powered by a silver oxide battery or a lithium battery.
However, these batteries are consumable supplies, and hence they need to be replaced periodically. In addition, the use of natural batteries leads to the consumption of limited natural resources and brings about environmental pollution when they are discarded.
To overcome these problems, wrist watches incorporating a power generation mechanism have been studied to replace battery-powered watches.
Known power generation mechanisms include a solar battery, a mechanical power generation mechanism and a thermoelectric power generation mechanism. The solar battery absorbs and converts the radiant energy of sunlight into electrical energy. The mechanical power generation mechanism utilizes gravitational energy. The thermoelectric power generation mechanism utilizes the Seebeck effect (the Peltier effect) based on a temperature difference. Of those mechanisms, watches powered by the solar battery and mechanical power generation have already been put in practical use.
On the other hand, the thermoelectric power generation mechanism is not yet commercially available although its principle has been known, as disclosed in Japanese Examined Patent Publication No. Hei 2-13279. It is still under study for practical use.
When thermoelectric power generation is utilized in a wrist-portable device, there is utilized a difference between the body temperature transferred to the wrist-portable device through the wrist (the high-temperature section) and the temperature of the air around the wrist-portable device (the low-temperature section).
However, the wrist-portable devices so far available have had problems of heat transfer from the high-temperature section to the heat receiving section of the thermoelectric generator and heat transfer from the radiation section of the thermoelectric generator to the low-temperature section, and these problems have prevented obtaining a temperature difference large enough to generate electric energy required for the thermoelectric generator.
The efficiency of radiation from the wrist-portable device to the outside air (low-temperature section) in particular fluctuates greatly, depending on how the wrist-portable device is worn or the like. For example, if part of the body is in contact with the radiation side of the wrist-portable device, the radiation section of the device does not radiate heat at all, and what is worse is that the radiation section absorbs heat, which is contrary to its purpose. Such problems may easily arise.